Generating energy from fluid expansion

A generator system for use in an organic Rankine cycle, comprising:

• a liquid reservoir for a working fluid of the organic Rankine cycle;
• a pump device coupled to the liquid reservoir to receive the working fluid from the liquid reservoir;
• an evaporator heat exchanger coupled to the pump device to receive the working fluid from the pump and apply heat to the working fluid;
• a turbine generator apparatus coupled to the evaporator heat exchanger to receive the working fluid from the evaporator heat exchanger and configured to generate electrical energy in response to expansion of the working fluid, the turbine generator apparatus comprising:
• an electric generator having a stator and a rotor,
• a first turbine having a first turbine wheel coupled to a first end of the rotor to rotate at the same speed as the rotor and configured to receive a working fluid into an inlet side of the first turbine wheel and output the working fluid from an outlet side of the first turbine wheel and rotate in response to expansion of the working fluid flowing from the inlet side to the outlet side of the first turbine wheel, wherein the first turbine is in fluid communication with the electric generator to direct at least part of the working fluid from the outlet side of the first turbine wheel in direct contact with the electric generator to cool the electric generator, and
• a second turbine having a second turbine wheel coupled to a second end of the rotor, opposite the first end of the rotor, to rotate at the same speed as the rotor, wherein the second turbine wheel is in fluid communication with the electric generator to receive the at least part of the working fluid from an outlet of the electric generator to an inlet side of the second turbine wheel;
• and
• a condenser heat exchanger coupled to the turbine generator apparatus to receive the working fluid from the turbine generator apparatus and extract heat from the working fluid.

A method of circulating a working fluid through a working cycle, comprising:

• vaporizing the working fluid;
• receiving the vaporous working fluid into an inlet side of a first turbine wheel;
• rotating the first turbine wheel in response to expansion of the working fluid through the first turbine wheel, and in turn rotating a rotor of an electric generator at the same speed as the first turbine wheel;
• outputting the working fluid from an outlet side of the first turbine wheel;
• receiving the working fluid from the outlet side of the first turbine wheel into an inlet side of a second turbine wheel disposed in a second turbine;
• rotating the second turbine wheel in response to expansion of the working fluid through the second turbine wheel, and in turn rotating the rotor at the same speed as the second turbine wheel;
• cooling the electric generator by directing at least part of the working fluid from an outlet side of the second turbine wheel in direct contact with the electric generator using the second turbine;
• and
• condensing the working fluid to a liquid.